Hi, Lex-
Thanks very much for your comments.
Yes, the blue color (I think more cyan as SCNR should have removed the green) is a mystery to me but all of my galaxies now show the same color using the PI ColorCalibration process for galaxies. I've grown to like it as different but it definitely is out of the range of what probably most people consider 'natural color'. I do note, however, that if you go to the PI home page,
http://pixinsight.com/you will see that all of the galaxies posted there from CAHA (m51,m74,ngc7331,m81/82) processed by our PTeam leaders, and many other galaxies posted there have the very same cyan cast to them. So I've attributed this to the PI galaxy color calibration method up to now.
The only other causes that I can think of in my processing are either the particular set of LRGB Astrondon Series I Gen2 filters that I use or perhaps the fact that I get most or all of my saturation increase in my PI processing (all target types) from lowering the Saturation setting in the LRGBCombination tool from the default 0.5. I've found that getting most of the color saturation from LRGBCombination gives me very colorful stars that I strive very much to obtain in my images (being very keen on getting a lot of color in my images). I should probably do some reprocessing testing without method to confirm it is the cause of the cyan color of all my galaxies but that is my current assumption.
Further thoughts on the matter would be appreciated, but as I said, I have grown to like this PI-galaxy color, if can generalize to say that.
Clear skies,
Jeff